changelog: prepare to automatize new rules entries

Use an empty item in the `New Rules` section as a marker for the GitHub
Action. If this causes problems, we could look into other solution such
as writing 2 lines before `### Bug Fixes`. But I think this is the
easiest I can come up with. So lets give it a try.

CHANGELOG.md

@@ -76,6 +76,7 @@ It includes many new rules, including all new techniques introduced in MITRE ATT
 - nursery/list-containers @williballenthin
 - nursery/run-in-container @williballenthin
 - persistence/registry/appinitdlls/disable-appinit_dlls-code-signature-enforcement @williballenthin
+-
 
 ### Bug Fixes
 

doc/release.md

@@ -24,7 +24,9 @@
 
     ### New Features
 
-    ### New Rules
+    ### New Rules (0)
+
+    -
 
     ### Bug Fixes